Skip to main content

Battery Desulfator Concept and Design Explored

Sulphation in lead acid batteries is quite common and a big problem because the process completely hampers the efficiency of the battery. Charging a lead acid battery through PWM method is said to initiate desulfation, helping recover battery efficiency to some levels.

What is Sulphation in Lead Acid Batteries

Sulphation is a process where the sulfuric acid present inside lead acid batteries react with the plates overtime to form layers of white powder like substance over the plates.

This layer deposit seriously deteriorates the chemical actions inside the battery while charging or discharging making the battery inefficient with its power delivering capabilities.

Normally this happens when the battery is not being used for long periods and the charging, discharging processes are not done very frequently.

Unfortunately there's no effective way of tackling this problem, however it has been researched that the jammed sulphur deposits over an effected battery may be broken down to some extent by subjecting the battery to high current bursts while charging it.

These high current charging pulses should be well optimized through some control circuit and should be diagnosed carefully while implementing the process.

Using PWM

Implementing the method through PWM controlled circuit is probably the best way of doing it.

Here's an excerpt from wikipedia, which says,

" Desulfation is achieved by high current pulses produced between the terminals of the battery. This technique, also called pulse conditioning, breaks down the sulfate crystals that are formed on the battery plates. Short high current pulses tend to work best. Electronic circuits are used to regulate the pulses of different widths and frequency of high current pulses. These can also be used to automate the process since it takes a long period of time to desulfate a battery fully."

The circuit of a PWM battery charger discussed here can be considered as the best design for carrying out the above desulfation process.

How the Circuit Functions

The IC 555 is configured and used in its standard PWM control mode.

The output from the IC is appropriately amplified through a couple transistors so that it is able to deliver the said high current pulses to the battery which needs to be desulfated.

The PWM control may be set at low "mark" ratio for implementing a desulfation process.

Conversely if the circuit is intended to be used for charging normal batteries, the PWM control may be adjusted for generating pulses with equal mark/space ratios or as per the desired specs.

The controlling of the PWM will solely depend on an individuals personal preference, so should be done correctly as per the battery manufacturers instructions.

Failing to follow the correct procedures may lead to fatal accidents with the battery, due to a possible explosion of the battery.

An input current level equal to the battery AH level may be chosen initially, and reduced gradually if a positive response is detected from the battery.

Desulfating with a Transformer and Bridge Rectifier Circuit

To make this simplest yet effective battery desulfator with charger circuit you would just require a suitably rated transformer, and a bridge rectifier. The design not only desulfates a battery, it keeps the new batteries from developing this issue and simultaneously charges them to the desired levels.

At the beginning of this post we learned how to desulfate using PWM concept, however a deeper research shows that the process of desulfating a battery may not necessarily require a precision PWM circuit, the supply just needs to be oscillating at some given rate, and that's enough to initiate the desulfating process (in most cases)... provided the battery is still within the curing range and is not beyond the reviving state.

So what would you need to make this super simple battery desulfator circuit which will also charge the given battery, and additionally possess the ability to keep the new batteries from developing the sulfation issue?

A suitably rated transformer, a bridge rectifier and an ammeter are all that's needed for the purpose.

The transformer voltage must be rated approximately 25% more than the battery voltage rating, that is for a 12V battery a 15 to 16V supply may be used across the battery terminals.

The current can be approximately equal to the AH rating of the battery for those which need to be revived and are badly sulfated, for the good batteries the charging current could be around 1/10th or 2/10th of  their AH rating. The bridge rectifier must be rated according to the specified or calculated charging levels.

Desulfator Schematic using Bridge Rectifier

Using a Full-Bridge Rectifier for Desulfation

The diagram above shows the bare minimum requirement for the proposed battery desulfator with charger circuit.

We can see the most standard or rather crude AC to DC power supply set up, where the transformer steps down the mains voltage to 15V AC for the specified 12V battery.

Before it can reach the battery terminals, the 15V AC goes through the rectification process through the attached bridge rectifier module and gets converted into a full-wave 15V DC.

With a 220V mains input, the frequency before the bridge would be 50Hz (standard grid spec), and after rectification this is supposed to become double that is at 100Hz. For a 110V AC input this would be around 120Hz.

This happens because the bridge network inverts the lower half cycles of the stepped down AC and combines it with the upper half cycles, to finally produce a 100Hz or 120 Hz pulsating DC.

It is this pulsating DC which becomes responsible for shaking-up or knocking down the sulfate deposits on the internal plates of the particular battery.

Using 100Hz Frequency

For a good battery this 100Hz pulsed charging supply ensures that the sulfation ceases to occur on the first place and thus helps to keep the plates relatively free from this issue.

You can also see an ammeter connected in series with the supply input, it provides a direct indication of he current consumption by the battery and provides a "LIVE update" of the charging procedure, and whether or not anything positive might be happening.

For good batteries this will provide the start to finish info regarding the charging process, that is initially the needle of the meter will indicate the specified charging rate by the battery and may be gradually expected to drop down to the zero mark, and that's when the charging supply needs to be disconnected.

A more sophisticated approach can be employed for enabling an automatic cut-off once the battery is fully charge by employing an opamp based automatic battery full charge cut off circuit (the second diagram)

Need Help? Please leave a comment, I'll get back soon with a reply!


  1. Good day, Swagatam,

    I didn't get nF capacitors (not available at the shop I went to), I bought a 1 microF and a 100 microF. If I substitute these into the circuit, how will it affect the output?


  2. Good day Satyam,

    The circuit needs to be operated with high frequency so a 1uF or 100uF will not work.

    1nf = 0.1uF, so can try other closer values like 0.22uF etc. or any value between 0.01uF to 0.1uF will also do.

  3. oops, correction: 1nF = 0.001uF

  4. better use a 680pF for pin6/2 and 103 or 0.01uF for pin5

  5. Good day,

    Thanks for your quick response. I've built the circuit with the components that I described, however I'll keep looking for the correct capacitors. (I got some surface-mounted caps yesterday, but destroyed them trying to install them.)

    I suspected that my frequency would be affected. Using f= 1/(0.693 x C x (R1 + 2R2)), the frequency of my circuit would be somewhere around 300 Hz, whereas your design is for 300 kHz. Does that sound about right?

    At any rate, I'm using it on a number of car batteries where I suspect sulphation. Will come back & update when I replace the caps, or with results.

    Best regards.

  6. Higher frequency would produce better effects according to me, however the pwm pulses would finally decide the optimization rate.

  7. Swagatam:
    Excellent circuit, I'm about to try arm. I'd appreciate if you tell me regularly cnveniente a zener and 100 ohm resistor voltage to the 555 and ensure it does not overheat.

    Thank you for your attention

  8. thanks electronica,

    the IC can work safely with upto 15V, yet for extra stabilization you may use a 7805 IC for it.

  9. Swagatam:


    Thanks for your reply and recommendation. If working at 555 with 5 volts regulated from 7805, the oscillation frequency is not affected?

    Are pleased to greet and congratulate again the excellent circuits published.

  10. Thanks Electronica,

    yes it will not be affected.

  11. Swagatam:
    Very nice, I appreciate your attention to my queries. Best wishes from Guatemala.


  12. Hi Swagatam, I have installed automatic voltage stabliser for home supply,
    the only problem is, when it starts, initialy it supply high volts(300 ) for less den 1 sec. den it functions well..
    Pls let me know what is the problem n how can i fix it..

  13. Hi Nawnit,

    You will need to add a delay ON timer at the output of your stabilizer as shown in the following link, a similar situation has been addressed at the bottom of the article.

  14. Thanks buddy,
    will it work fine upto 4 kw load?

  15. You will have to select the relay appropriately, I think a 30 amp relay would do the job.

  16. Thanks Swagat,
    sorry for one more problem,
    I inspected the stablizer, it has 24 volts relays, so i need to operate the "delay on" circuit on 24 volts instead 12 volts.
    What modification i need?

  17. You will have to use a 24V relay in the circuit, that's all, no other change would be required.

  18. The 24v supply for the circuit can be derived from the stabilizer board itself.

  19. Thanks Swagat,
    Tryed smthing diffrnt with the stablizer that i must share wid u.
    There are 5 taps in auto transformer, 1st n 3rd tap has been used as input with a relay control and rest for output wid 2 more relays.
    I inspected the 1st relay status at power on, it was making 1st tap as as input for 1 sec then change it to 3rd tap as input, so there was high volt at power on.
    I interchanged 1st and 3rd tap input with relay.
    Now its working good .

  20. But m not sure if it will be failed for high voltage input. Vl try to make a diagram of switching.
    Please comment.

  21. It's difficult to guess how it will do with high or low voltage condition, we can't say without practical testing, let's see...

  22. Hi Swagat,
    I need a signal strength meter for direct to home disc alignment at roof.
    Can it be made simply at home with transistor and led.

  23. Hi Nawnit,

    UHF Signal meters are complex devices, not within my reach.

  24. Thanks!

    The negative will go to the rail which is connected to pin#1 of the IC

  25. Hi Swagatam, your circuits are incredibly practical. Thanks for sharing and explaining.
    I am a bit confused as I read the thread as I saw reference to a 100K pot and L1 inductor but the circuit above for PWM 555 pulser does not show these. What am I missing ?


  26. Thank you Sean,

    Actually the circuit has gone through many changes since it was first posted, so please ignore the previous comments as those are with reference to the previous diagram which had quite a few flaws.
    The present design looks to be easier and viable.

  27. Thanks for your clarification. I was curious about the use of the inductor (i.e. collapsing magnetic field/pulse, etc).
    Anyhow, I will try this circuit out as its simple enough to make. I would like to try to revive some large capacity (100AH) NiMh batteries I have pulsing with high current. I am hoping the technique will lower the internal resistance of the batteries even though the chemistry is different (i.e. they don't sulphate).

  28. I wanted to keep it simple, so I eliminated the inductor part, I hope it works for you....:)

  29. Hi Swagatam
    Finally have parts to make the pwm but looking for a hi current supply.
    It occurred to me that lead acid batteries will not sink as much current as it starts to get full. Does the circuit take this into consideration ?
    When the transistor is on, is it essentially grounding the battery ?
    When it is off, is there any ringing without an inductor ?


  30. Hi Sean,

    If the voltage is set at some higher level then that will force the battery to sink the current which in turn will hopefully initiate the desulfation process.

    Here you can try with a 15V DC, current may be equal to the AH level of the battery and the pot set to provide short pulses.

    When the transistor is ON, it connects the negative of the battery to the negative of the power supply completing the circuit for the battery so that it receives the required charging pulse.

    No, there won't be any ringing effect due to the absence of an inductor.

  31. hi Swagatam,
    Thanks again for your reply. How do I limit the current ?
    I planned on using an old server power supply or rewinding the secondary of a microwave transformer. Won't the circuit try to pull all the current it can unless its limited ?

  32. Hi Sean,

    The circuit will not draw anything above 5mA, as long as the voltage does not exceed 15/16V mark, above this anyway the IC555 would get damaged, so I don't think any current control for the circuit would be required.

  33. Hi Swagatam, I think you mis-understood my question.
    With your circuit you recommend limiting the current to the battery initially to 1C. so if I have a 40AH battery, I should limit the pulse current to 40AH. I was asking how I could do this since I don't have a power supply with a current limit. I am thinking of making a power supply by stepping down 240VAC to 15VAC and rectifying it. But this will not be limited. Is there a clever way to control the max current the battery draws ?

  34. Hi Sean,

    You can select a transformer rated at around 20 to 30 amps, that will itself take care of the current...actually the current is not a critical value, anything higher than the normal charging method can be employed, and expected to work here.

  35. Thanks again Swagatam, will update the thread with my results.
    btw, I read somewhere (maybe here..) that the high current pulse may burn out shorted cells restoring even batteries that are considered unrepairable.

  36. Hi Sean,

    Then that would be an added feature of this design.

    Looking forward to your wishes!

  37. i am very proude of you . how can i indicate this circuit is working after design

  38. keep a voltmeter attached with the battry, if the voltage increases gradually within 4 hrs means it's working.

  39. please ignore these initial comments, the diagram has been modified and updated differently, so these comments have no relevance with the present diagram.

  40. Hi Swagatam

    I have read some of above posts talking about an inductor L1. Where is that inductor, I can't see it in the circuit or any reference in your article?

    By the way, I am working on a trickle charge desulfator. I am considering to integrate a circuit to measure battery's internal resistance (BIR). There are a few BIR measuring circuits on the net but, they need to take occasional measurement manually. Here are two of them:

    My idea is to have three-LED indication........the red LED to indicate high resistance, yellow to indicate medium and green for very low resistance. The BIR circuit will operate in parallel with the desulfator circuit. The illumination of the green LED would indicate that the battery has been desulfated, now it is ready to use.

    A relay could be used to connect the BIR circuit to the battery periodically to check the status. A latch can be deployed to keep the indicator LED on but, I just cannot sort out how to get the output on LED as the output is just 5-50mV.

    Can you please help me in this regard? If required, I can send you the links of the sites to have the description of those circuits.

  41. Hi Abu-Hafss,

    In the original design I had used an inductor but later found that it could be avoided and came up with the present design , the inductor related comments that you see were posted with reference to the earlier design

    A BIR could be a very useful ad-on.

    50mV can be amplified by using a opamp may be. What do you think?

  42. Hi Swagatam

    I came across a desulfator circuit which, apart from the regular desulfation process, also shorts momentarily battery terminals as shown here:

    I want to know, couldn't the signal from the 555 pin#3 be directly fed to the gate of the mosfet (point A) or at point B?

  43. Hi Abu-Hafss,

    How does this circuit it by charging and shorting the battery alternately? I could not understand the concept.

  44. Hi Swagatam :)

    One complete cycle includes 3 steps:

    1) 15 sec pulse charging
    2) 1 sec delay for settling
    3) 100ms shorting battery terminals

    I am just curious about the driving of the mosfet as I asked in my previous post.

  45. Hi Abu-Hafss :) how are these three steps implemented because i can see only one active input from the IC 555.

    I wanted to know the relevance of the transistor stages for answering your question correctly.

    Normally we know that a mosfet gate can be integrated with any IC output may it be a 555, a cmos or a opamp, as long as the voltage is below 15V

  46. Hi Swagatam

    Since I was focusing only on the mosfet so I didn't gave you the details of the other sections.

    As mentioned earlier, one cycle consists of mainly 3 steps + 1 step to monitor battery voltage. Each step is controlled by a 555 and another 555 is controlling all these 4 ICs (the entire cycle). If you want to have a look at the circuit, here it is.

    I am sorry, that is maximum available resolution of the picture.

    Now, I repeat my question in other way. If the mosfet can be driven directly by the 555, why the author deployed 0.8A transistors to drive the mosfet. You can find them at the top-right corner. I haven't linked the website as per your general instruction however, if you want to see the circuit description I can send you the link.

  47. Hi Abu-afss,

    It could be for allowing the mosfet to conduct and restrict correctly, especially the use of the push-pull (PNP/NPN) stage which ensures safe charge/discharge of the internal cap of the mosfet, because as we all know how sensitive these mosfets can be at times.

  48. Hello Swagatam,

    I would like to build a hi/lo adjustable relay/contactor.
    Say ....12v on 13.5 off
    I could then put it in series with any charger.
    It would be great for maintenance and prevent over charging.

    A variant of this could also kick in a discharge cycle.
    This would be good for desulfating.

    Do you have a design lik this?


  49. Hello Carl,

    Please see the last diagram in the following link, it'll fit your need well:

    The second relay shown is not relevant, you may remove it.

  50. Hi Swagatam

    Here is my basic design for LED indication of BIR status. The reference voltage is 12mV.

    But, later I realized that the output is is mVAC. Any suggestions, how to deal this issue?

  51. Hi Abu-Hafss,

    I am not able to recollect the previous discussions and the simulation made by me with reference to this diagram, so not able to figure out much about the circuit, if you can point out specific concerns in your diagram then probably I can try suggesting my opinions.

  52. Hi Swagatam

    Kindly refer to my post of January 12, 2014. Here is the link for your ready reference.

    The battery internal resistance is measured in mVAC. A good battery would show less than 12mVAC. And with higher internal resistance would show more than 12mVAC.

    I am just wondering how to compare the fluctuating mVAC with a reference voltage.

  53. Hi Abu-Hafss,
    I think it would be a better idea to use a LM3915 IC for detecting the relevant voltage levels because the opamp circuit could become too complex.
    Refer to the last diagram in the following article, the mic can be removed and the transistor may be directly fed from the 100k pot output

  54. how can i indigate this is working correctly irf 540 get heat?

  55. Lead Lead Sulfate PbSO4 is part of battery charge discharge cycle. The structural form of PbSo4 makes the difference. While amorphous PbSo4 is reversible while hard crystalline PbSO4 is irreversible and inactive. Shallow cycle batteries never have to be discharged under 12.5 volts. If this happens an immediate charge will consume and transform PbSO4 in to Pb, H2O, PbO2 and H2So4. If let staying there for sometime the PbSO4 crystallize and turns inactive. To make a long story short if battery isn’t in use immediately use Float charging with a battery trickle. Harbor freight tools sell a battery trickle (Floater) for $9.99, which I bought on sale for $6.0. The manufacturer 13.2Volts was only a promise, but replacing VR1 with a 100-Ohm trim pot, I can adjust the voltage from 12.6V to 14.25V. I set it at 13.25V but this is only the first aid. What you need is EQUALIZE the BATTERY; this can be done at 14.5V for some hours. During this process the strong cells start boiling but the weakest cells continue charging. This can be done with a battery tender. I bought one from Wal-Mart connected to my VW Touareg and the next day the relay was chattering ON / OF non-stop. Measured Voltage a found 14.85 Volts. The electronic system of the car was fighting hard against this stupid tender. I solved the problem building up my Battery Tender with precision voltage Window 14.5V stop charging and 12.6V restart charging giving the battery a chance to rest, RELAX. Charging a discharged battery you have to deal with Bulk Charge Current Density that depends from electrode surface and is expressed on mA / Cm2. If a have to deal with an accidentally fully discharged battery I use my Automatic Smart Battery Charger, with Equalizing and reconditioning features.

  56. hi
    I just realise in the circuit there is no ground to the circuit?
    if we use power supply to connect to this circuit the plus 15V pole goes to the battery and the circuit where then the negative pole goes?
    I know if I use coil and transistor I have to connect the negative pole to emitter but on mos fet not sure looks like this one joint missing from the circuit
    could you please correct me if I am wrong?

  57. The line connected with pin#1 of the IC is the negative line and must be connected with the power supply negative.

  58. So Avenger is saying that there is no coming back from hard crystalline PbSO4 .
    One should have all batteries under full time trickle charge.

    Avenger ,.... which one of Swagatam's designs did you use for your charger?


  59. thank you I already done it just downloaded the ic pin out then I know the number 1 leg is the ground.
    thank you again for your fast response and attention.

  60. Is it possible to desulphate my 6v,5ah sealed lead acid battery by this ckt.

  61. How it to be possible?what changes in the ckt for 6v,5ah sla battery desulphating.and how much time taken to desulphate.

  62. use 10V supply with 3 amp current,
    use TIP122 instead of the mosfet
    time is not known....... also the result may not be positive, will depend on how much your battery may be recoverable.

  63. Thanks for your information.tell me the Pin connections of TIP122 while using instead of mosfet in this ckt.

  64. Hi Mr. Swagatam, newbee here.
    So I've finished assembling the circuit, how to tell that it's working before I start attaching it to the battery? I mean is there some type of indication there or do i've to measure anything first?
    thank you.

  65. Hi Imanul,

    There's no circuit which can guarantee a perfect desulfation in dead batteries, so you can only hope that this circuit produces the intended results as it's designed as per the standard recommended specifications.

    Use the circuit for about 4 hours and then check the battery with an appropriate load, if the charge sustains for an appreciable amount of time you can assume it to be revived, otherwise you may repeat the procedure with some change in the PWM frequency and/or the input current to the circuit and check the response in a similar manner.

  66. ...please change the 1n caapcitor with a 10uF capacitor.

    connect an LEd across pin3 and ground via a 1K resistor.

    When switched ON this LED must flash rapidly indicating a proper functioning of the circuit, changing the pot would change the flash rate on this LEd

    you can keep the new capacitor connected and use the circuit for the required purpose, it won't make any difference in the performance.

  67. Hi,

    I started building your old circuit and only realized you have changed them ,but I have bought parts for the old diagram,so can I build the circuit without the inductor with the TIP122 ,or should I Change it IRF540.

  68. I've built the first circuit and when i connect the battery the coil heats up and smokes

  69. Hi, I changed the circuit a long time ago may be a half year ago, it's strange you are building it now.

    I would recommend you to make the above shown design instead of the earlier one since adding a coil will not make much of a difference.

  70. please try the above circuit without the coil, the TIP122 will need to be upgraded if your battery AH is higher than 20AH

  71. Can I use IRF540N instead of IRF540

  72. IRF540N will do and will work for an 80AH battery

  73. can we ad two LEDs to show it is charging and one for it is charged?

  74. Hi swagatam! Is there a need to change some parts of the circuit if my battery is ranging 7 to 14 amp?

  75. Hi swagatam! What is the ideal mosfet for a below 20amp battery?

  76. Hi Josue,

    no changes would be required for your mentioned application.

  77. IRF540 is the ideal mosfet as shown in the diagram

  78. Hi Mikel,

    you can connect an LED across pin3 and ground with a series 1K resistor but it will appear continuously glowing due to high frequency pulses from the IC

  79. Thanks Mikel,

    changing 1nF to 1uF will reduce the frequency or the pulse rate, but that will not affect the results, so it's OK.

    the mosfet and the supply voltage are also OK, but the current input must be well over 20 amps for desulfating a 100AH battery, so make sure the supply current is at this level.

  80. Sir, I'm planning to add this circuit on my existing 72v ebike charger. It has 6 pcs.12v 20ah battery connected in series. Would it be possible? What ic regulator should I use for LM555's supply voltage? And what mosfet would you recommend?

  81. Hi Jusi, yes you can try it, just make sure to disconnect the battery positive from the shown point and connect it with the +72V supply........and connect the positive of the circuit with the positive of last 12V battery in the series which has its negative connected with the bike's ground or the bike's negative....

    the negative of the circuit can be joined with this ground that is the common ground line.

  82. Thanks Sachin,

    shorting would be advisable only if the battery has sufficient charge on it, unless it's charged fully, shorting won't induce any effect on the plates.

    The pulse charger explained in the above article is the ultimate way of dealing with this mess, if the battery responds and wakes up to the pulsed charging only then the shorting of the terminals can be tried, however as shown in the video a high amp resistive load would be more appropriate than shorting since here we don't have to worry about the delay period in ms

  83. Good day to you sir.
    Thank you for sharing all the great work.
    A few questions about this circuit :
    1. What is the 5k POT for ? & how to adjust it ?
    2. Does the IRF 540 need a heat sink ?
    3. The negative of charger is directly connected to IC Pin #1 ?
    4. How to connect a LED to this circuit, that illuminate when connect to battery ?
    5. Any harm if connect to the battery permanently ?
    Thanks a lot in advance .

  84. Good day Alaa,

    1) 5K is for playing with the output pulse width, which might in turn help to implement a optimal desulfating could be a matter of some trial and error and dependant on the connected battery condition. however it's not so crucial, you can keep it at the center to begin with

    2) Normally it shouldn't require a heatsink, however you can test it practically by touching it, to be on a safer side..

    3) yes the negative of the charger needs toeb connected to the pin#1 line of the IC

    4) charging indication might not be possible, however an ammeter may be connected in series with the battery positive to get a direct reading regarding the batt response to the charging procedure.

    5) yes if the battery begins responding and ammeter can be used for monitoring the same as explained in the above point

  85. which simulator i can use to make this circuit and can have a dead battery in it for charging?
    if you plz don't mind...can you plz send me the whole process from the begining till the battery desulphation.. what all the pins are doing ... plz .. i will be gratefull to you.

  86. simulation is not required, just procure the parts and the build the circuit, the circuit is explained in the articles itself...

  87. is there any inductor on the above schematic ????

  88. Interesting circuit. I had a thought, perhaps this could be combined with adding a very small (<3ml) of acid to each cell technique for unmucking dead SLAs typically run to death in UPSs.
    If they are at 0.0V I doubt any technique will work but its the ones which have good voltage but next to no capacity that could be salvageable.

  89. thanks for updating this info, appreciate it!

  90. hi mr swagatam,i hope you are good
    i suggest to add a simple mosfet driver using a transistor cause 555 output voltage is weak and thus will overheat the mosfet,i tried before to connect 555 output to mosfet gate with a resistor and mosfet gets hot.

  91. cause mosfet need at least 5v to operate normally.
    best regrads

  92. Hi Hisham, I am good thanks,

    555 IC has an output that's more powerful than most ICs, however mosfets never require a powerful signal to operate, they just need a voltage above 9V for operating optimally.

    You can try reducing the gate resistor to 10 ohms and check the response....or may be the load you have connected could be above the mosfet range

  93. IC 555 will produce a voltage that's exactly equal to the supply voltage, so in the above case the output will be 15V at pin3...not an issue for the mosfet.

  94. Can we use this circuit for sealed lead acid battery 6 volts please reply

  95. can i use irf640 instead of irf540.....or is it work without toroid coils which are arranged in order to make hi pluses.. that is 1000uH and 200uH

  96. torroid coil is not necessary....i am not sure about IRF640, if its current/voltage specs are compatible then it can be used

  97. Hi swagatam please i need your help i have a 12v battery@200A and they are 4 in number connected in parallel and i want to make a charger for it, a charger that provide at least 80A for the battery connected in parallel please can you give me pulse width charger circuit with cut off that can handle such high current thanks

  98. Hi Faith, the 80 amp is supposd to come from the transformer of the charger power can use any relay based automatic charger posted in this website and attach a 14V 100 amp power supply to its input for achieving the required results.

  99. Please can u give me the link to relay base automatic charger

  100. you can try the following

  101. sir, i want use led for pulse show in this circuit where i connect please help

  102. connect it from pin#3 to ground through a 1K resistor, but the LED will appear continuously lit with any frequency higher than 4Hz

  103. I just build it, but not work and then checked using an oscilloscope nothing pulse or voltage spike Yo the battery.
    Adivice me, give solving about this problem.

  104. it means your 555 is not working or a is faulty, replace the 5K pot with 100K and replace the pin6/2 capacitor with a 100uF, and check the output if it generates the pulses or not...if still not, then you may think about changing the IC

  105. Sir I'm really proud of you for ur good works and quik response you are one in a million. Sir about the above circuit can it be use to charge a 12v@600AH and if yes what modifications should i do. secondly the circuit seem not to have charge control which means one needs to monitor the so that it dont get over charge if that be the case how can i add a cut of can i use this circuit from this your post if yes how i attached it

  106. Thank you Faith,

    you can use the above circuit for charging any desired battery, through appropriate modifications in the mosfet value.

    for your application you will need to replace the existing mosfet with a 100amp rated moefet...

  107. Thank u for the reply

    Ok can connect mosfet in parallel so that the current can be shared among them.

    secondly the circuit seem not to have charge control which means one needs to monitor the battery so that it dont get over charge if that be the case how can i add a cut of can i use this circuit from this your post

    Again is the mosfet N-channel or p-channel

    If N-channel is it the drain that gose to the negative of the battery? While source to ground

  108. Again should my duty cycle be 95% or 100% advice is needed in this case

  109. yes connecting the mosfets in parallel will also work to increase the amps.

    I won't recommend the linked 555 based design, instead you ca use the following one

    the mosfet shown in the above desulfator article is an N channel, and its source is connected with the negative line.

  110. duty cycle can be a matter of experimentation , start with 50% initially

  111. Hi you are the best
    I made this charger and its really working thank you very much please how do i include cutoff to this circuit

  112. thanks Faith, you can use the following circuit for the cut off


  113. Sir this what i observe i noticed that even when there is no gate voltage to the mosfet the battery is still charging i went as far removing the 555timer to confirm this and notice the battery was charging please what could be the cause and how to correct it thanks

  114. Faith, I think your mosfet is already burnt, or was originally faulty....instead you can try a TIP35 BJT, because BJTs are normally more rugged than mosfets and do not get burnt mysteriously...

  115. Sir please answer me let know way forward

  116. I have already answered, please press the "load more" button to the hidden comments

  117. Faith,

    I think you are not able see my replies because you are not pressing the "load more" button....unless you do this you won't be able to see the hidden replies.

    your second question is very strange, and It can be difficult for me to figure out the solution until I check the circuit practically...

  118. it is not shown by mistake, but it's understood, otherwise how the circuit will work?

  119. Hi Mr. Swagatam, thanks for the very good information all over the site. I have an AC to 24v DC transformer and would like to know how to get the voltage down to 15v and can I then use that? Your help is much appreciated.

  120. Hi Peter, you can add 12 to 14nos of 1N5408 diodes in series with the positive line, this will drop the 24V to 15V

  121. Thanks Swag,
    If I understand it is 12 1N 5408 in series?


  122. Hi Mr. Swag,
    Hopefully the last question. Can I use a 7815 voltage regulator instead of the diodes? What would be advantages /disadvantages.

    Many thanks

  123. Hi Peter, you can use 7815, but it will allow only upto 1 amp current for the battery....

  124. Thanks a lot. I will use that until I can get the diodes.

  125. Hi Mr Swag,
    I have now built the circuit with the diodes in series, but find that the diodes get very hot after about 10 minutes. The Ic and mosfet however do not. Is this normal?
    I have checked for solder bridges and found none. Input to the diodes is 20vdc and to battery pos 15.2 VDC. Output from the mosfet drain is 12.4VDC. Any help will be appreciated.

  126. Hi Peter, which diodes did you use? check the current consumption during the charging with a series ammeter and make sure to use diodes that is rated 2 times more than this measured current consumption

  127. Hi Mr. Swag,
    Thanks for the reply. I used the 1n5408 diodes in series. Would I measure the current at the output of the Mosfet or the output from the diodes?

  128. Hi Peter, you can connect the meter in series with the positive supply line ...anywhere.... the current must pass through the meter, that's the requirement.

  129. hello sir Swag .. is the circuit above whether it can be connected with car alternator with 60 Ah battery and if required fuse. thanks (sorry I use google translation ?)

  130. Hello Edy, it may be possible if the alternator output is suitably rectified, filtered and regulated at around 15V

  131. Thanks Mr. Swag


Post a Comment